Motronic High Voltage Tests

1. Remove distributor cap and inspect.
a. Remove upper cover and spark plug wires from cap.
b. Using a 32mm wrench, unscrew the nut that holds the fan to the water pump (left hand threads!), and remove the fan.
c. Remove the three bolts that secure the distributor cap to the front cover (8mm heads), and remove the cap.
d. Inspect the cap for signs of cracking, burning, carbon tracking, corroded terminals, missing center carbon contact, etc.
e. Replace as necessary.

2. Remove distributor rotor and inspect.
a. With distributor cap removed, remove rotor by unscrewing the three socket head securing bolts with a 3mm allen wrench.
b. Check resistance between center and end contacts. Resistance should be 1000 Ohms ± 20%.
c. Inspect resistor (red compound section between contacts) for signs of cracking, or burning.
d. Inspect bakelite portion of rotor for cracking, chipping, or burning.
e. Replace rotor as necessary, tightening rotor to adapter bolts to 2.8 ± 0.2 Nm (2 ± 1 ft/lb).

3. Remove ignition wires and inspect.
a. Inspect the connectors at both ends of the wires for corrosion, bad or missing spring clips, and wire/connector connection.
b. Inspect insulation by bending wire in a tight radius and looking for cracks.
c. Check the resistance of the wires. Resistance should be:
Angled caps at coil and distributor 1000 Ohms ± 20%
Shielded spark plug connectors 5000 Ohms ± 20%
Note; BMW uses solid core wire with screw on resistors at each end. Because of this, all wires should have about the same resistance, regardless of length (compared to carbon core wire in which the resistance increases with the length of the wire).